Rotating disc magnetic recording systems typically employ magnetic head transducers which glide over the magnetic disc media on a cushion of air. The mounting or support structure which carries the transducers are termed “sliders.” Sliders have air-bearing surfaces that are propelled off the surface of moving media by boundary air which moves with the media disc. The air-bearing surface of a slider is aerodynamically designed to glide on the boundary air due to a pattern of raised rails and recesses which establish the “fly height” of the slider. Read/write transducers are mounted on the rear side of the slider, with the reader sensor and writer gap at the air-bearing surface, facing the moving media.
A slider assembly typically includes a ceramic slider and associated read/write heads, a support flexure arm, interconnection wires between the heads and external signaling devices, and any associated mounting hardware. The slider assembly is mounted on an arm which is movable over the surface of a rotating magnetic disc to position the slider adjacent selected tracks on the disc. Disc drives usually employ multiple discs which rotate together, spaced apart from one another on a single spindle. One slider assembly is provided for each magnetic recording surface in a disc drive.
In magnetic disc drive data storage devices, digital data are written to and read from a thin layer of magnetizable material on a surface of one or more rotating discs. Write and read operations are performed through the write and read transducers. The slider and transducers are sometimes collectively referred to as a head, and typically a single head is associated with each disc surface. When the read transducer is a magnetoresistive (MR) type sensor, the combination of the slider and the transducer are frequently referred to as a MR head. The head is selectively moved under the control of electronic circuitry to any one of a plurality of circular, concentric data tracks on the disc surface by an actuator device. Each slider body includes an air bearing surface (ABS). As the disc rotates, the disc drags air beneath the ABS, which develops a lifting force that causes the head to lift and fly above the disc surface.
As with many electronic elements, a slider assembly, also known as a head gimbal assembly, is sensitive to electrostatic discharge that can result from electrostatic charges accumulating on a surface of the slider assembly. The most common sources of electrostatic charges in the production, testing and use of disc drive components such as head gimbal assemblies are humans and machines. Electrostatic discharge is a particular issue when testing head gimbal assemblies.
When the charge becomes sufficiently strong to overcome the insulating properties of any materials that are between the charged surface and another surface having a lower electrical potential, an electrostatic discharge occurs. As is well known in the art, electrostatic discharges can be devastating to electronic components, which is why for example individuals who install or replace circuit boards within a PC are often instructed to ground themselves to a metal surface within the chassis of the PC.
As disc drives progress in terms of storage space and access speed, they become increasingly sensitive to electrostatic discharge, and they become increasingly sensitive to electrostatic discharge occurring at ever decreasing voltages. A need remains for structure and methods of protecting electronic elements such as head gimbal assemblies from electrostatic discharge.
The present invention provides a solution to this and other problems, and offers other advantages over the prior art.